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As a popular open source development project, Python has an active
supporting community of contributors and users that also make their software
available for other Python developers to use under open source license terms.

This allows Python users to share and collaborate effectively, benefiting
from the solutions others have already created to common (and sometimes
even rare!) problems, as well as potentially contributing their own
solutions to the common pool.

This guide covers the installation part of the process. For a guide to
creating and sharing your own Python projects, refer to the
distribution guide.

Note

For corporate and other institutional users, be aware that many
organisations have their own policies around using and contributing to
open source software. Please take such policies into account when making
use of the distribution and installation tools provided with Python.

pip is the preferred installer program. Starting with Python 2.7.9, it
is included by default with the Python binary installers.

a virtual environment is a semi-isolated Python environment that allows
packages to be installed for use by a particular application, rather than
being installed system wide

virtualenv is a third party tools for creating virtual environments, it
is defaults to installing pip into all created virtual environments.

the Python Packaging Index is a public repository of
open source licensed packages made available for use by other Python users

the Python Packaging Authority are the group of
developers and documentation authors responsible for the maintenance and
evolution of the standard packaging tools and the associated metadata and
file format standards. They maintain a variety of tools, documentation
and issue trackers on both GitHub and
BitBucket.

distutils is the original build and distribution system first added to
the Python standard library in 1998. While direct use of distutils is
being phased out, it still laid the foundation for the current packaging
and distribution infrastructure, and it not only remains part of the
standard library, but its name lives on in other ways (such as the name
of the mailing list used to coordinate Python packaging standards
development).

The standard packaging tools are all designed to be used from the command
line.

The following command will install the latest version of a module and its
dependencies from the Python Packaging Index:

python -m pip install SomePackage

Note

For POSIX users (including Mac OS X and Linux users), the examples in
this guide assume the use of a virtual environment. You may install
virtualenv to provide such environments using either pip
(pipinstallvirtualenv) or through your system package manager
(commonly called virtualenv or python-virtualenv).

For Windows users, the examples in this guide assume that the option to
adjust the system PATH environment variable was selected when installing
Python.

It’s also possible to specify an exact or minimum version directly on the
command line. When using comparator operators such as >, < or some other
special character which get interpreted by shell, the package name and the
version should be enclosed within double quotes:

A number of scientific Python packages have complex binary dependencies, and
aren’t currently easy to install using pip directly. At this point in
time, it will often be easier for users to install these packages by
other means
rather than attempting to install them with pip.

On Linux systems, a Python installation will typically be included as part
of the distribution. Installing into this Python installation requires
root access to the system, and may interfere with the operation of the
system package manager and other components of the system if a component
is unexpectedly upgraded using pip.

On such systems, it is often better to use a virtual environment or a
per-user installation when installing packages with pip.

Python has typically relied heavily on source based distribution, with end
users being expected to compile extension modules from source as part of
the installation process.

With the introduction of support for the binary wheel format, and the
ability to publish wheels for at least Windows and Mac OS X through the
Python Packaging Index, this problem is expected to diminish over time,
as users are more regularly able to install pre-built extensions rather
than needing to build them themselves.

Some of the solutions for installing scientific software
that is not yet available as pre-built wheel files may also help with
obtaining other binary extensions without needing to build them locally.